Music compensation for active noise control systems
A vehicle includes a music signal processing system having a loudspeaker disposed within a passenger compartment of the vehicle and emitting audible music into the passenger compartment. A microphone is disposed within the passenger compartment and converts the audible music and noise within the passenger compartment into an analog electrical microphone signal. An analog-to-digital converter is connected to an output of the microphone and receives the analog electrical microphone signal and converts the analog electrical microphone signal into a digital electrical microphone signal. A sample rate down converter is connected to an output of the analog-to-digital converter. A narrow band adaptive noise control is connected to an output of the sample rate down converter and receives an engine speed signal. A sample rate up converter is connected to an output of the narrow band adaptive noise control. An adder device adds an output of the sample rate up converter to a music signal. A digital-to-analog converter is connected to an output of the adder device. An amplifier has an input connected to an output of the digital-to-analog converter. An output of the amplifier is connected to an input of the loudspeaker.
1. A vehicle including a music signal processing system comprising:
a loudspeaker disposed within a passenger compartment of the vehicle and configured to emit audible music into the passenger compartment;
a microphone disposed within the passenger compartment and configured to convert the audible music and noise within the passenger compartment into an analog electrical microphone signal;
an analog-to-digital converter connected to an output of the microphone and configured to receive the analog electrical microphone signal and convert the analog electrical microphone signal into a digital electrical microphone signal;
a sample rate down converter connected to an output of the analog-to-digital converter, the sample rate down converter being configured to perform multi-rate processing, the sample rate down converter including a means to decrease a number of operations performed per second to emit the audible music;
a narrow band adaptive noise control connected to an output of the sample rate down converter and configured to receive an engine speed signal;
a sample rate up converter connected to an output of the narrow band adaptive noise control;
an adder device configured to add an output of the sample rate up converter to a music signal;
a digital-to-analog converter connected to an output of the adder device; and
an amplifier having an input connected to an output of the digital-to-analog converter, an output of the amplifier being connected to an input of the loudspeaker.
2. The vehicle of claim 1 wherein the sample rate down converter includes:
a filter connected to an output of the analog-to-digital converter; and
a decimator connected to an output of the filter.
3. The vehicle of claim 1 further comprising a filter included in the sample rate down converter, the narrow band adaptive noise control, or the sample rate up converter.
4. The vehicle of claim 1 wherein the noise within the passenger compartment includes periodic engine noise whose dominant frequency is directly related to the engine speed.
5. A vehicle including a music signal processing system, comprising:
a narrow band adaptive noise control configured to receive an engine speed signal;
a sample rate up converter connected to an output of the narrow band adaptive noise control;
a first adder device configured to add an output of the sample rate up converter to a music signal;
a digital-to-analog converter connected to an output of the first adder device;
an amplifier having an input connected to an output of the digital-to-analog converter;
a loudspeaker disposed within a passenger compartment of the vehicle and having an input connected to an output of the amplifier, the loudspeaker being configured to emit audible music into the passenger compartment;
a microphone disposed within the passenger compartment and configured to convert the audible music and noise within the passenger compartment into an analog electrical microphone signal;
an analog-to-digital converter connected to an output of the microphone and configured to receive the analog electrical microphone signal and convert the analog electrical microphone signal into a digital electrical microphone signal;
a first sample rate down converter connected to an output of the analog-to-digital converter;
a processor receiving the music signal and configured to perform a second transformation on the music signal, the second transformation being an estimate of a first transformation performed on the music signal by the digital-to-analog converter, the amplifier, the loudspeaker, the microphone and the analog-to-digital converter;
a second sample rate down converter connected to an output of the processor; and
a second adder device configured to subtract an output of the second sample rate down converter from an output of the first sample rate down converter, the narrow band adaptive noise control receiving an output of the second adder device.
6. The vehicle of claim 5 wherein the first sample rate down converter includes:
a first low pass filter connected to an output of the analog-to-digital converter; and
a first decimator connected to an output of the first low pass filter; and
the second sample rate down converter includes:
a second low pass filter connected to an output of the processor; and
a second decimator connected to an output of the second low pass filter.
7. The vehicle of claim 5 wherein each of the first sample rate down converter and the second sample rate down converter is configured to perform multi-rate processing.
8. The vehicle of claim 7 wherein each of the first sample rate down converter and the second sample rate down converter comprises a means to decrease a number of operations performed per second to emit the audible music.
9. The vehicle of claim 5 wherein a windowed filter is included in the first sample rate down converter, the second sample rate down converter, the narrow band adaptive noise control, and/or the sample rate up converter.
10. The vehicle of claim 5 wherein a truncated filter is included in the first sample rate down converter, the second sample rate down converter, the narrow band adaptive noise control, and/or the sample rate up converter.
11. The vehicle of claim 5 wherein the noise within the passenger compartment includes periodic engine noise whose dominant frequency is directly related to the engine speed.